In the present study, the aim is to choice of appropriate catalyst and operation conditions for maximizing the bio-oil yields. The upgrading of the rapid pyrolysis vapors was carried out with various catalysts (Clinoptilolite (NZ), ZSM-5, H-Y) under different conditions in a dual reactor. Both natural and synthetic zeolites were investigated for upgrading of pyrolysis vapors with various catalyst/feed ratios (C/F) when the second stage held at 400oC. The catalytic treatment with synthetic zeolites provided...